Make HRH::IsKeepAlive() look past the first header

Up until now, HttpResponseHeaders::IsKeepAlive() only looked at the
first value of the Connection header. Since for a WebSocket response a
header like

Connection: Upgrade, close

is valid we should check other values past the first value.

BUG=371759
TEST=net_unittests

Review URL: https://codereview.chromium.org/640213002

Cr-Commit-Position: refs/heads/master@{#300087}

net/http/http_response_headers.cc

@@ -1202,28 +1202,40 @@ bool HttpResponseHeaders::GetTimeValuedHeader(const std::string& name,
   return Time::FromUTCString(value.c_str(), result);
 }
 
+// We accept the first value of "close" or "keep-alive" in a Connection or
+// Proxy-Connection header, in that order. Obeying "keep-alive" in HTTP/1.1 or
+// "close" in 1.0 is not strictly standards-compliant, but we'd like to
+// avoid looking at the Proxy-Connection header whenever it is reasonable to do
+// so.
+// TODO(ricea): Measure real-world usage of the "Proxy-Connection" header,
+// with a view to reducing support for it in order to make our Connection header
+// handling more RFC 7230 compliant.
 bool HttpResponseHeaders::IsKeepAlive() const {
-  if (http_version_ < HttpVersion(1, 0))
-    return false;
-
   // NOTE: It is perhaps risky to assume that a Proxy-Connection header is
   // meaningful when we don't know that this response was from a proxy, but
   // Mozilla also does this, so we'll do the same.
-  std::string connection_val;
-  if (!EnumerateHeader(NULL, "connection", &connection_val))
-    EnumerateHeader(NULL, "proxy-connection", &connection_val);
+  static const char* kConnectionHeaders[] = {"connection", "proxy-connection"};
+  struct KeepAliveToken {
+    const char* token;
+    bool keep_alive;
+  };
+  static const KeepAliveToken kKeepAliveTokens[] = {{"keep-alive", true},
+                                                    {"close", false}};
 
-  bool keep_alive;
+  if (http_version_ < HttpVersion(1, 0))
+    return false;
 
-  if (http_version_ == HttpVersion(1, 0)) {
-    // HTTP/1.0 responses default to NOT keep-alive
-    keep_alive = LowerCaseEqualsASCII(connection_val, "keep-alive");
-  } else {
-    // HTTP/1.1 responses default to keep-alive
-    keep_alive = !LowerCaseEqualsASCII(connection_val, "close");
+  for (const char* header : kConnectionHeaders) {
+    void* iterator = nullptr;
+    std::string token;
+    while (EnumerateHeader(&iterator, header, &token)) {
+      for (const KeepAliveToken& keep_alive_token : kKeepAliveTokens) {
+        if (LowerCaseEqualsASCII(token, keep_alive_token.token))
+          return keep_alive_token.keep_alive;
+      }
+    }
   }
-
-  return keep_alive;
+  return http_version_ != HttpVersion(1, 0);
 }
 
 bool HttpResponseHeaders::HasStrongValidators() const {

net/http/http_response_headers_unittest.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include <algorithm>
+#include <iostream>
 #include <limits>
 
 #include "base/basictypes.h"
@@ -1640,6 +1641,14 @@ struct KeepAliveTestData {
   bool expected_keep_alive;
 };
 
+// Enable GTest to print KeepAliveTestData in an intelligible way if the test
+// fails.
+void PrintTo(const KeepAliveTestData& keep_alive_test_data,
+             std::ostream* os) {
+  *os << "{\"" << keep_alive_test_data.headers << "\", " << std::boolalpha
+      << keep_alive_test_data.expected_keep_alive << "}";
+}
+
 class IsKeepAliveTest
     : public HttpResponseHeadersTest,
       public ::testing::WithParamInterface<KeepAliveTestData> {
@@ -1714,6 +1723,82 @@ const KeepAliveTestData keepalive_tests[] = {
     "proxy-connection: keep-alive\n",
     true
   },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: Upgrade, close\n",
+    false
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: Upgrade, keep-alive\n",
+    true
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: Upgrade\n"
+    "Connection: close\n",
+    false
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: Upgrade\n"
+    "Connection: keep-alive\n",
+    true
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: close, Upgrade\n",
+    false
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: keep-alive, Upgrade\n",
+    true
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: Upgrade\n"
+    "Proxy-Connection: close\n",
+    false
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: Upgrade\n"
+    "Proxy-Connection: keep-alive\n",
+    true
+  },
+  // In situations where the response headers conflict with themselves, use the
+  // first one for backwards-compatibility.
+  { "HTTP/1.1 200 OK\n"
+    "Connection: close\n"
+    "Connection: keep-alive\n",
+    false
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Connection: keep-alive\n"
+    "Connection: close\n",
+    true
+  },
+  { "HTTP/1.0 200 OK\n"
+    "Connection: close\n"
+    "Connection: keep-alive\n",
+    false
+  },
+  { "HTTP/1.0 200 OK\n"
+    "Connection: keep-alive\n"
+    "Connection: close\n",
+    true
+  },
+  // Ignore the Proxy-Connection header if at all possible.
+  { "HTTP/1.0 200 OK\n"
+    "Proxy-Connection: keep-alive\n"
+    "Connection: close\n",
+    false
+  },
+  { "HTTP/1.1 200 OK\n"
+    "Proxy-Connection: close\n"
+    "Connection: keep-alive\n",
+    true
+  },
+  // Older versions of Chrome would have ignored Proxy-Connection in this case,
+  // but it doesn't seem safe.
+  { "HTTP/1.1 200 OK\n"
+    "Proxy-Connection: close\n"
+    "Connection: Transfer-Encoding\n",
+    false
+  },
 };
 
 INSTANTIATE_TEST_CASE_P(HttpResponseHeaders,